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The magazine will keep publishing online as a single, worldwide edition called Newsweek Global, with the shift to an all-digital format after 80 years in print set to start in early 2013.

"We are transitioning Newsweek, not saying goodbye to it," Newsweek and Daily Beast editor-in-chief Tina Brown wrote Thursday on The Daily Beast. "We remain committed to Newsweek and to the journalism that it represents."

Newsweek will produce its last U.S. print edition for the Dec. 31 issue and plans to support Newsweek Global on tablets, e-readers and the web with paid subscriptions. Some Newsweek content will be available on the The Daily Beast, which is also owned by the magazine’s parent company IAC.

Brown wrote that "regrettably" there would be layoffs as a result of streamlining editorial and business operations in the U.S. and overseas. She said the move "is an extremely difficult moment for all of us who love the romance of print."

In a note to staff, Brown and Daily Beast CEO Baba Shetty wrote: "We realize news of a big change like this will be unsettling. We wish to reassure you the transition is well planned, extremely mindful of the unavoidable impact on our staff and respectful of our readers, advertisers and business partners."

Newsweek's losses have reportedly run about $40 million a year, according to The New York Times. The magazine's print circulation has tumbled 51 percent since 2007, industry website Poynter.org reported, citing the publisher’s statement filed with the Audit Bureau of Circulations.

Newsweek's move to drop its print edition wasn't entirely unexpected. Back in July, IAC head Barry Diller hinted during an earnings call that the publication would become digital only.

In announcing the change, Brown wrote that Newsweek content has helped drive a 70 percent increase in unique visitors to The Daily Beast website over the past year.

She wrote that tablet users in the U.S. were expected to top 70 million this year, up from 13 million two years ago.

"In our judgment, we have reached a tipping point at which we can most efficiently and effectively reach our readers in all-digital format," Brown wrote. "This was not the case just two years ago. It will increasingly be the case in the years ahead."